Magnetic flowmeter assembly with zero-flow measurement capability

Abstract

A system and related method for operating a magnetic flowmeter. The method includes driving a first coil assembly with a first coil drive and a second coil assembly with a second coil driver to a zero (0) electrical potential. Then measuring a residual voltage in the conductive fluid using a pair of electrical electrodes. The residual voltage corresponding to a zero-flow measurement error. Correcting an induced voltage measurement detected by the pair of electrical electrodes when the first and second coil assemblies are driven to non-zero electrical potentials. The corrected voltage measurement determined by subtracting the zero-flow measurement error from the induced voltage measurement. Lastly, determining a corrected fluid velocity based on the corrected voltage measurement. The corrected fluid velocity measurement accounting for the zero-flow measurement error

What is claimed is: 
     
         1 . A method for operating a magnetic flowmeter, the flowmeter configured to measure a velocity of a conductive fluid in a flow path, the method comprising:
 driving a first coil assembly and a second coil assembly to a zero (0) current to prevent a magnetic field from forming in the fluid flow path;   measuring a zero-flow measurement value in the fluid flow path, the zero-flow measurement value occurring when the first and second coil assemblies are at the zero (0) current;   correcting a voltage measurement by subtracting the zero-flow measurement value from an induced voltage detected by a pair of electrical electrodes when the first coil assembly and the second coil assembly are driven by a non-zero current; and   determining a corrected fluid velocity measurement from the corrected voltage measurement, the corrected fluid velocity being corrected for the zero-flow measurement value.   
     
     
         2 . The method as defined in  claim 1 , wherein driving the first coil assembly and second coil assembly to a zero (0) current comprises not driving the first coil assembly with a first drive current and not driving the second coil assembly with a second drive current. 
     
     
         3 . The method as defined in  claim 1 , wherein measuring a zero-flow measurement value in the fluid flow path comprises measuring a residual voltage with a pair of electrical electrodes located perpendicular to the fluid flow path. 
     
     
         4 . The method as defined in  claim 1 , wherein correcting a voltage measurement comprises driving the first coil assembly and second coil assemblies with non-zero currents such that the magnitude of the voltage inducted by the first coil assembly equals the magnitude of the voltage induced by the second coil assembly. 
     
     
         5 . The method as defined in  claim 1 , further comprising monitoring the zero-flow measurement value to detect changes of the conductive fluid's electrical potential. 
     
     
         6 . The method as defined in  claim 1 , further comprising monitoring the zero-flow measurement value to detect performance changes of the magnetic coil assemblies. 
     
     
         7 . The method as defined in  claim 1 , further comprising monitoring the zero-flow measurement value to detect grounding changes of the conductive fluid. 
     
     
         8 . A device for controlling a magnetic flowmeter, the magnetic flowmeter configured to measure the velocity of a conductive fluid in a flow path, the device comprising:
 a first coil assembly circuit configured to generate a first magnetic field proximate the fluid flow path, the first coil assembly circuit comprising:
 a first coil assembly; 
 a first voltage source configured to provide a first voltage output; and 
 a first coil driver configured to provide a first drive current to the first coil assembly based on the first voltage output; 
   a second coil assembly circuit configured to generate a second magnetic field proximate the flow path, the second coil assembly circuit comprising:
 a second coil assembly; 
 a second voltage source providing a second voltage output; and 
 a second coil driver configured to provide a second drive current to a second coil assembly based on the second voltage output; 
   a pair of electrical electrodes configured to detect a voltage signal proximate the fluid flow path; and   a computer processor configured to:
 determine a zero-flow measurement value in the fluid flow path by driving the first and second voltage sources to a zero (0) electrical potential and measuring a residual voltage in the fluid flow path using the pair of electrical electrodes; 
 correct a voltage value by subtracting the zero-flow measurement value from an induced voltage, the induced voltage being detected by the pair of electrical electrodes when the first and second voltage sources are driven to non-zero electrical potentials; and 
 calculate a corrected fluid velocity value from the corrected voltage value, the corrected fluid velocity value adjusted for the zero-flow measurement value. 
   
     
     
         9 . The device as defined in  claim 8 , wherein the computer processor drives the first and voltage sources to non-zero potentials such that the magnitude of the voltage inducted in the first coil assembly equals the magnitude of the voltage induced in the second coil assembly. 
     
     
         10 . The device as defined in  claim 8 , wherein the computer processor is further configured to monitor the zero-flow measurement value to detect performance changes of the magnetic coil assemblies. 
     
     
         11 . The device as defined in  claim 8 , wherein the computer processor is further configured to monitor the zero-flow measurement value to detect grounding changes of the fluid media. 
     
     
         12 . The device as defined in  claim 8 , wherein the computer processor is further configured to monitor the zero-flow measurement value to detect changes in the conductive fluid's electrical potential. 
     
     
         13 . A non-transient computer readable storage medium comprising computer executable instructions that when executed by a computer processor performs a method, comprising:
 driving a first coil assembly and a second coil assembly to a zero (0) current thereby preventing a magnetic field from forming in the fluid flow path;   detecting a zero-flow measurement value in the fluid flow path using a pair of electrical electrodes, the measurement value being detected when the first and second coil assemblies are at zero (0) current;   determining a corrected voltage measurement by subtracting the zero-flow measurement value from an induced voltage value detected by the pair of electrical electrodes when the first coil assembly is driven by a first drive current and the second coil assembly is driven by a second drive current; and   calculating a corrected fluid velocity value from the corrected voltage measurement, the corrected fluid velocity value compensating for the zero-flow measurement value.   
     
     
         14 . The non-transient computer readable storage medium as defined in  claim 13 , wherein driving the first coil assembly and the second coil assembly to a zero (0) current comprises not driving the first coil assembly with a first drive current and not driving the second coil assembly with a second drive current. 
     
     
         15 . The non-transient computer readable storage medium as defined in  claim 13 , wherein determining a corrected voltage measurement comprises driving the first coil assembly and second coil assembly with non-zero currents such that the magnitude of the voltage inducted in the first coil assembly equals the magnitude of the voltage induced in the second coil assembly. 
     
     
         16 . The non-transient computer readable storage medium as defined in  claim 13 , further comprising monitoring the zero-flow measurement value to detect changes the conductive fluid's electrical potential. 
     
     
         17 . The non-transient computer readable storage medium as defined in  claim 13 , further comprising monitoring the zero-flow measurement value to detect performance changes of the magnetic coil assemblies. 
     
     
         18 . The non-transient computer readable storage medium as defined in  claim 13 , further comprising monitoring the zero-flow measurement value to detect grounding changes of the conductive fluid.